As a command input device used for mobile information devices which place the importance on the portability, such as mobile phones, PDAs (Personal Digital Assistants), and notebook PCs, and mobile information devices which places the importance on the display units such as displays, desired is a device whose command input unit on the device is reduced in size.
As a method for reducing a key layout space of the command input unit on the device, there is considered a function of allotting a plurality of functions to a single input. As a method of such kind, for example, Patent Document 1 proposes a method which places a joystick on the device for detecting tilt angles in the top-and-bottom as well as left-and-right directions, and switches characters according to the tilt directions. However, it is required to get accustomed to operations for adjusting the tilt directions of the joystick for executing each input, so that the input operations become complicated. This may also cause input errors.
Further, Patent Document 2 also discloses a method which places a plurality of optical sensors that are independent from keys on an input unit, and allots input processing functions according to combinations of operation states of the optical sensors. However, as in the case of the method that utilizes the key combination operations, this method also faces complication of the operation itself.
Further, there is also a method which places a detection unit in a place different from a display unit such as a display. As such method, as disclosed in Patent Document 3, known is a method which places a tactile input protrusion unit on a back-face side of a reference terminal, and executes an input by applying a pressure. However, a display space is required within the display unit in order to check the input positions, so that it is necessary to increase the size of the display. Therefore, this method is not suited for reducing the size of the device itself. Further, the pitch of the input areas is narrow, so that it is difficult to set the input positions, etc.
Further, there is a method which individually places a detection unit separately from a device. As such method, there have been proposed devices which execute input operations by loading a detection unit to a human body, as disclosed in Patent Document 4, Patent Document 5, and Patent Document 6. However, it is necessary to prepare an input unit separately from the device, so that the portability thereof is poor. Further, it gives a troublesome feeling for operators who are required to wear the detection unit.
Furthermore, as an input module utilizing vibrations, there is known a type which detects a tapping operation conducted by a user, and automatically performs prescribed input processing that corresponds to strength levels and intervals of the tapping operation, as disclosed in Patent Document 7. However, since it is necessary to select a desired processing operation by adjusting the strength level and the interval of the tapping operation, it is still necessary for the user to have a specific skill.
Patent Document 1: Japanese Unexamined Patent Publication 2005-301874
Patent Document 2: Japanese Unexamined Patent Publication Hei 2-113317
Patent Document 3: Japanese Unexamined Patent Publication 2003-162362
Patent Document 4: Japanese Patent Application Publication 2004-537802
Patent Document 5: Japanese Unexamined Patent Publication Hei 11-338597
Patent Document 6: Japanese Unexamined Patent Publication 2007-128304
Patent Document 7: Japanese Unexamined Patent Publication 2002-190857